1. Field of the Invention
The present invention relates to a method for authenticating an interactive recording medium such as an interactive DVD (IDVD) or an enhanced navigation DVD (ENAV DVD).
2. Description of the Related Art
High-density optical disks capable of recording large amounts of data are being widely used. The Digital Versatile Disc (DVD), which is a recording medium that is capable of recording large amounts of high-quality video data as well as digital audio data, is one example of these high-density optical disks.
Interactive optical disk such as IDVDs and ENAV DVDs are now under development. An interactive optical disk stores various ENAV applications such as characters, other movies, animations, or dubbed audio related to the main A/V stream that is being reproduced and thus allows a user to select and reproduce an ENAV application along with the main A/V stream. The ENAV DVD comprises a DVD video zone storing main A/V data and other zones storing ENAV applications data related to the main A/V data.
An optical disk player capable of playing ENAV DVDs comprises a DVD playback engine for reproducing the main A/V stream and an ENAV engine for reproducing the ENAV applications in synchronization with the main A/V stream and for controlling the DVD playback engine from time to time. If an ordinary DVD is loaded into the ENAV DVD player, the main A/V stream recorded thereon is reproduced only by the DVD playback engine. If an ENAV DVD is loaded, the main A/V stream and relevant ENAV applications are reproduced by the interaction of the DVD playback engine and the ENAV engine.
The ENAV DVD player is expected to be able to utilize various contents data in addition to the ENAV applications data recorded on an ENAV DVD by connecting to a remote contents server through the Network and downloading contents data relevant to the ENAV DVD, which extends the range of application services of the ENAV DVD and helps overcome the limit of disk capacity.
Due to the advent of new rewritable recording media such as DVD-R, DVD-RW, DVD+RW, and DVD-RAM, ENAV DVDs are exposed to illegal copying of contents. Also, concern about attempts to copy the contents of ENAV DVDs to hard disk drives is increasing.
In case of an ordinary DVD, the DVD player is required to judge whether the DVD is an illegal copy. In case of an ENAV DVD, not only the DVD player but the server to which the DVD player attempts to connect is required to authenticate the ENAV DVD inserted into the DVD player.
Contents providers, who provide through the network contents data needed for reproducing ENAV applications recorded on ENAV DVDs, want to examine whether clients attempting to access their contents servers to download contents data (e.g., users of ENAV DVD players or PCs having ENAV DVD drives installed therein) use authenticated DVDs or illegal copies. A contents server, therefore, will allow a client to access it only when the client's ENAV DVD is a genuine product and block the access if the client's ENAV DVD turns out to be an illegal copy.
Methods for determining whether a recording medium inserted into an ENAV DVD player attempting to access a remote server that provides contents data is a genuine product are under discussion. In general, a disk player attempting to access a remote server is requested to transmit to the server the ENAV disk ID (hereinafter referred to as ENAV DiskID) or the signature of sector raw data (hereinafter referred to as SSRD) of the disk loaded into the player.
Such authentication methods, in particular, specific authentication procedures needed between a disk player and a contents server are required. However, an effective solution or standard is not yet available.
In order to judge whether an ENAV DVD loaded into the ENAV DVD player attempting to access the contents server is a genuine product, the contents server requests that the ENAV DVD player provide information on the ENAV DVD, i.e., ENAV DiskID or SSRD corresponding to a particular logical sector number (hereinafter referred to as LSN) of the ENAV DVD specified by the contents server.
The ENAV DiskID is commonly recorded at an initial position that can be accessed first when the disk is inserted into the disk player for reproduction. The server-specified LSN may be arbitrary in the data area of the disk.
If the disk authentication is requested before the reproduction of the main A/V stream or ENAV applications begins, it is no problem to move the optical pickup of the disk player to a position from which the authentication data can be obtained. However, if the disk authentication is requested in the middle of the reproduction of the main A/V stream or ENAV applications, the movement of the optical pickup for obtaining the authentication data causes the reproduction to stop temporarily.
Even in the middle of the reproduction of the main A/V stream or ENAV applications, the disk player may connect to the server to obtain required contents data according to the viewer's request. In this case, the viewer may tolerate the suspension of the reproduction caused by the attempt to obtain the authentication data because he/she made the request.
On the other hand, while the main A/V stream or an ENAV application is being reproduced or after the reproduction of an ENAV application is completed, contents data for a next ENAV application may be required. In this case, the disk player attempts to connect to the contents server to obtain the required data, which makes the reproduction of the main A/V stream stop temporarily. This situation is not what the viewer can expect and prepare for and thus may frustrate the viewer.
Whether the main A/V stream or ENAV applications can be reproduced seamlessly depends on various factors, such as when the contents sever performs the authentication process, the authentication data type that the contents server requests from the disk player, and whether the authentication process is performed on a server basis or on a universal resource identifier (hereinafter referred to as URI) basis. The URI represents the individual position of each of the stored contents data file within the server.
For a stable and seamless playback of the main A/V stream or ENAV applications, a new method for authenticating an ENAV DVD to be performed by the contents server and the disk player is required.